introduce lxc-snapshot

Hopefully someone else will come in and spruce it up :)  This
version is as simple as can be

lxc-snapshot -n a1
	create a snapshot of a1
echo "second commit" > /tmp/a
lxc-snapshot -n a1 -c /tmp/a
	create a snapshot of a1 with /tmp/a as a commit comment
lxc-snapshot -n a1 -L
	list a1's snapshots
lxc-snapshot -n a1 -L -C
	list a1's snapshots along with commit comments
lxc-snapshot -n a1 -r snap0 a2
	restore snapshot 0 of a1 as container a2

Some easy nice-to-haves:

1. sort snapshots in the list
2. allow a comment to be given in-line
3. an option to remove a snapshot?

Removing a snapshot can just as well be done with

	lxc-destroy -P /var/lib/lxcsnaps/c1 -n snap2

so I leave it to others to decide whether they really want
it, and provide the patch if so.

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>

src/lxc/Makefile.am

@@ -171,7 +171,8 @@ bin_PROGRAMS = \
 	lxc-config \
 	lxc-destroy \
 	lxc-create \
-	lxc-user-nic
+	lxc-user-nic \
+	lxc-snapshot
 
 if HAVE_NEWUIDMAP
 bin_PROGRAMS += lxc-usernsexec
@@ -207,6 +208,7 @@ lxc_unshare_SOURCES = lxc_unshare.c
 lxc_wait_SOURCES = lxc_wait.c
 lxc_kill_SOURCES = lxc_kill.c
 lxc_create_SOURCES = lxc_create.c
+lxc_snapshot_SOURCES = lxc_snapshot.c
 lxc_usernsexec_SOURCES = lxc_usernsexec.c
 lxc_user_nic_SOURCES = lxc_user_nic.c
 

src/lxc/lxc_snapshot.c

@@ -0,0 +1,201 @@
+/*
+ *
+ * Copyright © 2013 Serge Hallyn <serge.hallyn@ubuntu.com>.
+ * Copyright © 2013 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "../lxc/lxccontainer.h"
+
+#include <stdio.h>
+#include <libgen.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <sys/types.h>
+
+#include <lxc/lxc.h>
+#include <lxc/log.h>
+#include <lxc/bdev.h>
+
+#include "arguments.h"
+#include "utils.h"
+
+lxc_log_define(lxc_snapshot, lxc);
+
+char *newname;
+char *snapshot;
+
+#define DO_SNAP 0
+#define DO_LIST 1
+#define DO_RESTORE 2
+int action;
+int print_comments;
+char *commentfile;
+
+int do_snapshot(struct lxc_container *c)
+{
+	int ret;
+
+	ret = c->snapshot(c, commentfile);
+	if (ret < 0) {
+		ERROR("Error creating a snapshot");
+		return -1;
+	}
+
+	INFO("Created snapshot snap%d\n", ret);
+	return 0;
+}
+
+void print_file(char *path)
+{
+	if (!path)
+		return;
+	FILE *f = fopen(path, "r");
+	char *line = NULL;
+	size_t sz = 0;
+	if (!f)
+		return;
+	while (getline(&line, &sz, f) != -1) {
+		printf("%s", line);
+	}
+	if (line)
+		free(line);
+	fclose(f);
+}
+
+int do_list_snapshots(struct lxc_container *c)
+{
+	struct lxc_snapshot *s;
+	int i, n;
+
+	n = c->snapshot_list(c, &s);
+	if (n < 0) {
+		ERROR("Error listing snapshots");
+		return -1;
+	}
+	if (n == 0) {
+		printf("No snapshots\n");
+		return 0;
+	}
+	for (i=0; i<n; i++) {
+		printf("%s (%s) %s\n", s[i].name, s[i].lxcpath, s[i].timestamp);
+		if (print_comments)
+			print_file(s[i].comment_pathname);
+		s[i].free(&s[i]);
+	}
+	free(s);
+	return 0;
+}
+
+int do_restore_snapshots(struct lxc_container *c, char *snap, char *new)
+{
+	if (c->snapshot_restore(c, snapshot, newname))
+		return 0;
+
+	ERROR("Error restoring snapshot %s", snapshot);
+	return -1;
+}
+
+static int my_parser(struct lxc_arguments* args, int c, char* arg)
+{
+	switch (c) {
+	case 'L': action = DO_LIST; break;
+	case 'r': snapshot = arg; action = DO_RESTORE; break;
+	case 'c': commentfile = arg; break;
+	case 'C': print_comments = true; break;
+	}
+	return 0;
+}
+
+static const struct option my_longopts[] = {
+	{"list", no_argument, 0, 'L'},
+	{"restore", required_argument, 0, 'r'},
+	{"comment", required_argument, 0, 'c'},
+	{"showcomments", no_argument, 0, 'C'},
+	LXC_COMMON_OPTIONS
+};
+
+
+static struct lxc_arguments my_args = {
+	.progname = "lxc-create",
+	.help     = "\
+--name=NAME [-w] [-r] [-t timeout] [-P lxcpath]\n\
+\n\
+lxc-create creates a container\n\
+\n\
+Options :\n\
+  -L, --list          list snapshots\n\
+  -C, --showcomments  show snapshot comments in list\n\
+  -c, --comment=file  add file as a comment\n\
+  -r, --restore=name  restore snapshot name, i.e. 'snap0'\n",
+	.options  = my_longopts,
+	.parser   = my_parser,
+	.checker  = NULL,
+};
+
+/*
+ * lxc-snapshot -P lxcpath -n container
+ * lxc-snapshot -P lxcpath -n container -l
+ * lxc-snapshot -P lxcpath -n container -r snap3 recovered_1
+ */
+
+int main(int argc, char *argv[])
+{
+	struct lxc_container *c;
+	int ret = 0;
+
+	if (lxc_arguments_parse(&my_args, argc, argv))
+		exit(1);
+
+	if (my_args.argc > 1) {
+		ERROR("Too many arguments");
+		return -1;
+	}
+	if (my_args.argc == 1)
+		newname = my_args.argv[0];
+
+	if (lxc_log_init(my_args.name, my_args.log_file, my_args.log_priority,
+			 my_args.progname, my_args.quiet, my_args.lxcpath[0]))
+		exit(1);
+
+	if (geteuid()) {
+		if (access(my_args.lxcpath[0], O_RDWR) < 0) {
+			fprintf(stderr, "You lack access to %s\n", my_args.lxcpath[0]);
+			exit(1);
+		}
+	}
+
+	c = lxc_container_new(my_args.name, my_args.lxcpath[0]);
+	if (!c) {
+		fprintf(stderr, "System error loading container\n");
+		exit(1);
+	}
+
+	switch(action) {
+	case DO_SNAP:
+		ret = do_snapshot(c);
+		break;
+	case DO_LIST:
+		ret = do_list_snapshots(c);
+		break;
+	case DO_RESTORE:
+		ret = do_restore_snapshots(c, snapshot, newname);
+		break;
+	}
+
+	lxc_container_put(c);
+
+	exit(ret);
+}